Simple Nature - Light and Matter

ExercisesExercise 2A: Reasoning with Ratios and PowersEquipment:ping-pong balls and paddlestwo-meter sticksYou have probably bounced a ping pong ball straight up and down in the air. The time betweenhits is related to the height to which you hit the ball. If you take twice as much time betweenhits, how many times higher do you think you will have to hit the ball? Write down yourhypothesis:Your instructor will first beat out a tempo of 240 beats per minute (four beats per second),which you should try to match with the ping-pong ball. Measure the height to which the ballrises:Now try it at 120 beats per minute:Compare your hypothesis and your results with the rest of the class.Exercise 2B: The Shell TheoremThis exercise is an approximate numerical test of the shell theorem. There are seven massesA-G, each being one kilogram. Masses A-E, each one meter from the center, form a shape liketwo Egyptian pyramids joined at their bases; this is a rough approximation to a six-kilogramspherical shell of mass. Mass G is five meters from the center of the main group. The class willdivide into six groups and split up the work required in order to calculate the total gravitationalenergy of mass G.1. Each group should write its results on the board in units of picojoules, retaining six significantfigures of precision.2. The class will add the results and compare with the result that would be obtained with theshell theorem.126 Chapter 2 Conservation of Energy